Date Published: November 27, 2008
Publisher: BioMed Central
Author(s): Susanne Löfgren, Stina Ekman, Ylva Terelius, Ronny Fransson-Steen.
This study was performed to characterize a gene-addition transgenic mouse containing a BAC (bacterial artificial chromosome) clone spanning the human CYP2C18&19 genes (tg-CYP2C18&19).
Hemizygous tg-CYP2C18&19, 11 week old mice were compared with wild-type littermates to obtain information regarding clinical status, clinical pathology and anatomical pathology. After one week of clinical observations, blood samples were collected, organs weighed, and tissues collected for histopathology.
In males, the tissue weights were lower in tg-CYP2C18&19 than in wild-type mice for brain (p ≤ 0.05), adrenal glands (p ≤ 0.05) and brown fat deposits (p ≤ 0.001) while the heart weight was higher (p ≤ 0.001). In female tg-CYP2C18&19, the tissue weights were lower for brain (p ≤ 0.001) and spleen (p ≤ 0.001) compared to wild-type females. Male tg-CYP2C18&19 had increased blood glucose levels (p ≤ 0.01) while females had decreased blood triglyceride levels (p ≤ 0.01).
Despite the observed alterations, tg-CYP2C18&19 did not show any macroscopic or microscopic pathology at the examined age. Hence, these hemizygous transgenic mice were considered to be viable and healthy animals.
The human cytochrome P450 enzymes from the 2C subfamily (CYP2C) are fairly well characterized and are known to metabolise many clinically important drugs. Four members belonging to the CYP2C family are found in man, namely CYP2C8, CYP2C9, CYP2C18 and CYP2C19 . The anticancer drug paclitaxel is metabolised by CYP2C8 and the 6-hydroxylation of this compound is commonly used as a marker for this enzyme . CYP2C9 metabolises many drugs, for example the hypoglycaemic drug tolbutamide , the anticonvulsant phenytoin [3,4], the anticoagulant warfarin  and a number of nonsteroidal anti-inflammatory drugs including diclofenac and ibuprofen , which have all been used as marker substrates. The CYP2C18 protein has not yet been found in detectable amounts in any tissues , and its in vivo function is, to date, unknown. CYP2C19 stereo-selectively metabolises the S-enantiomer of the anticonvulsant mephenytoin to the metabolite 4-hydroxy- (S)-mephenytoin , and this metabolite is commonly measured to determine CYP2C19 activity in vitro. The 5-hydroxylation of R-omeprazole is selectively performed by CYP2C19  and this reaction is also occasionally used as marker reaction for CYP2C19. A variety of other substrates are known to be metabolised by CYP2C19, such as the biguanide antimalarials , certain barbiturates , the β-blocker propranolol , the anxiolytic diazepam  and the antidepressant imipramine .
The regulation and functions of the members of the CYP2C family are complex with large variations in expression within, and between, different tissues. The humanized mouse model characterized in this paper may facilitate the study and understanding of the functions of the human CYP2C enzymes. The demonstrated alterations in organ weights and clinical chemistry parameters cannot all be explained with the current knowledge of the CYP2C enzymes.
In the present study a gene-addition transgenic mouse, containing a BAC spanning the human CYP2C18&19 genes, has been characterized. Some alterations in organ weight and clinical pathology parameters were observed. Despite the alterations, no pathological changes were observed macroscopically or histologically and these hemizygous tg-CYP2C18&19 mice were considered to be viable and healthy. Hopefully, this model could be used to investigate the roles of CYP2C18 and CYP2C19 in vivo and extrapolation of results obtained from studies with this model may be more predictive to humans than when using traditional animal models.
The authors declare that they have no competing interests.
SL carried out the pathological evaluation of the study, participated in the design of the study, performed the statistical analysis and drafted the manuscript. SE and YT helped to draft the manuscript. R F-S helped to draft the manuscript and funded the study. SE, YT and R F-S have all been supervisors to SL during the course of the study.